Well, Rampage obviously agreed to go through with it, so in my mind those concerns you just shared must not be a very big deal to him. Maybe the belt isn't everything to some people, anyway. Maybe he just wants to stomp a mudhole in Rashad's ass, the LHW belt be damned.
I'm just going off of what we do know for a fact. That is-
1) Dana wants to keep Rampage as busy as possible so he doesn't get tied up in any crap outside of "work"
2) Rampage agreed to coach on TUF and do these fights
3) Rampage wants to fight Rashad Evans.... badly.
All three of those are satisfied with this deal, and that is what we DO know. The things you say are all "what ifs". So, arguing from a logical standpoint it seems to make perfect sense. I understand your questions, but again- I'd rather go with the facts than guesses.
EDIT: Maybe reading this
will help clarify. I just saw it posted on Yahoo! news, and it seems to go along with this plan pretty well. Rampage isn't stupid- he knows he's going to have to become a student of the game to beat Machida. Not only that, the dude's got angst. He wants to crush Rashad. Plus, he gets to spend time with his family and heal up from nagging injuries. Like I have been saying from the beginning- I don't see how it doesn't make sense. This article with quotes from Rampage shows exactly that. It's always better to go with the facts than to go with speculation.